Two major technologies are in use today to monitor radiation exposure from ionizing radiation. The technologies are generally categorized as passive, or delayed readout, dosimetry and active, or real time, dosimetry. Passive dosimeters have included, for example, TLD-based dosimeter elements, bubble-based dosimeter elements, polycarbonate-based dosimeter elements, photographic film-based dosimeter elements, indium-based dosimeter elements, sulphur-based dosimeter elements, quartz-based dosimeter elements or gold-based dosimeter elements, or the like. Active dosimeters have used, for example, silicon diodes, photodiodes, GM tubes, ionization chambers, electrets, MOSFETs and DRAMs, or the like, as the radiation sensitive elements for providing real time monitoring of radiation levels.
The two different technologies each have advantages and drawbacks not associated with the other. For example, TLD (thermoluminescence dosimetry) can be used to satisfy strict performance requirements demanded by various governmental bodies or other entities that cannot be fully met by active dosimeters presently available in the marketplace. On the other hand, TLD does not lend itself to real time monitoring of radiation whereas as active dosimeters are commonly used today as indicators to provide a warning when radiation exposure exceeds a prescribed level.